In Chapter 4, the narrator and Maxim begin spending a lot of time together. The way she begins describing their relationship foreshadows the strangeness of their eventual marriage:
As he watched me into the lift I thought of yesterday, Mrs. Van Hopper’s chattering tongue, and his cold courtesy. I had ill-judged him, he was neither hard nor sardonic, he was already my friend of many years, the brother I had never possessed.
Maxim is much older than the narrator, who reminds the reader often that she was barely an adult at this time. He begins taking her out for long drives that she keeps secret from Mrs. Van Hopper. They aren't yet doing anything especially scandalous, but the narrator also struggles to describe exactly what they are doing. Their relationship grows deep and codependent incredibly fast. Having just met Maxim, she describes him as "already my friend of many years, the brother I had never possessed." Both a brother and a friend of many years are closer companions than Maxim can possibly be at this point, and yet neither one is a romantic partner. Today, we might describe Maxim's behavior as "grooming" because he is crossing social boundaries and leaving the narrator feeling special but confused about where she stands with him.
While du Maurier paints a picture of an unhealthy, obsessive bond developing between Maxim and the narrator, the novel is less interested in the way Maxim takes advantage of the narrator than in the way this strange relationship will develop into a stage for the melodrama of Rebecca's life and death. Maxim and the narrator can't have a straightforward courtship because in many ways, Maxim is still married to Rebecca. The narrator's roundabout way in this passage of defining the relationship she is developing with him foreshadows the difficulty she will have fitting herself into the role of "Mrs. de Winter." That title belongs to Rebecca. The narrator's attempt to claim it will bring memories of Rebecca rushing back to everyone at Manderley, reinforcing that the narrator is an imposter in her own marriage—not a wife, but a hanger-on. Only when Maxim confesses to the narrator that he killed his first wife do they truly start acting like they are married. The narrator proves herself Rebecca's equal by helping Maxim cover up the murder. Perversely, before they can be romantic partners, they must be partners in crime.
In Chapter 6, the narrator pores over a book of poems Maxim has given her, excited to think that it might mean he is falling in love with her. She is disturbed to find that the title page bears an inscription "to Max from Rebecca," and she rips it out; what she does next foreshadows the end of novel:
I took a box of matches and set fire to the fragments. The flame had a lovely light, staining the paper, curling the edges, making the slanting writing impossible to distinguish. The fragments fluttered to gray ashes. The letter R was the last to go, it twisted in the flame, it curled outwards for a moment, becoming larger than ever. Then it crumpled too; the flame destroyed it. It was not ashes even, it was feathery dust… I went and washed my hands in the basin. I felt better, much better.
The narrator tries not to care about the fact that the book has a note from Rebecca. After all, she reminds herself, the woman is dead. What threat can she pose to the narrator's burgeoning relationship with Maxim? Try as she might, however, the narrator cannot stop obsessing over the inscription. She is especially unsettled by Rebecca's "curious, sloping letters" and blobs of ink, which turn the message into physical evidence that Rebecca's hand touched this page. Tearing the page up and throwing it away is not enough. The narrator feels compelled to burn it.
It is not only the fire, but also the way the narrator describes the flames that foreshadows the fire Mrs. Danvers sets to Manderley. Time seems to slow down as she watches the flames eat the paper bit by bit. She finds the sight enrapturing and stares at it, just as she and Maxim stare at Manderley while it burns on the horizon in the final scene. The large letter R, Rebecca's first initial, is symbolic. As the last thing to disappear, it evokes the way Rebecca herself resists erasure from Manderley and from Maxim's life. The R even grows larger before it disintegrates. Similarly, by burning Manderley down to avenge Rebecca's murder, the housekeeper turns Rebecca's legacy into a spectacular blaze on the horizon. Rebecca may be dead, but she gets to take Manderley down with her.
Even though the house is lost, there is the possibility that the fire might be a relief. Manderley would always have been haunted by Rebecca's memory. The way the narrator literally washes her hands of the title page and feels "better, much better" foreshadows a fire that clears everyone's conscience. But the narrator's anxiety over Rebecca eventually comes creeping back in, at Monte Carlo and at Manderley. Likewise, the anxious dream that opens Chapter 1 has already established that Rebecca did not stop haunting the narrator or Maxim after Manderley burned down. For better or worse, Rebecca is indelibly inscribed on both of their memories.
In Chapter 13, the narrator explores the harbor and finds a buoy with the name "Je Reviens" inscribed on it. This name, and the narrator's reflection on it, foreshadows the discovery of Rebecca's boat and body a few chapters later:
“Je Reviens”—“I come back.” Yes, I suppose it was quite a good name for a boat. Only it had not been right for that particular boat which would never come back again.
As the narrator notes, "je reviens" is French for either "I come back" (as in, "I make a habit of coming back") or "I am coming back" (as in, "I am on my way back right now"). This phrase is a clear harbinger of Rebecca's return, although the narrator does not realize it yet. She pauses on this name because in general, English boats are more likely to be named after either women or abstract concepts such as "liberty" or "memory." It is less common for them to have a whole sentence or idiom as a name. She realizes as she thinks about it that French boats sometimes have common expressions for names, and she ultimately decides that "I come back" is a fitting name for a boat. It is almost like a good luck charm. Generally speaking, people want their boats to come back after each voyage.
Still, the narrator thinks that an exception would be Rebecca's boat: that boat has failed to come back in the most spectacular way. At the same time, the narrator is not exactly correct that Rebecca's boat has failed to come back. Even if it is still physically absent, there is no doubt that it has a presence at Manderley. People think about Rebecca and her boat every day. The narrator cannot escape them. In an abstract sense, the idea that Rebecca's boat has failed to return already appears to be wishful thinking.
The phrase "Je Reviens" is a hint to the reader and the narrator that not only are Rebecca and her boat lingering at Manderley in spirit, but they are also going to return physically before long. Once the diver discovers the boat at the bottom of the harbor, Rebecca's presence will be undeniable. While Rebecca can't actually speak from beyond the grave, the phrase "Je Reviens" might as well have been her dying words. She manipulated Maxim into murdering her to make sure that even though she was dying of cancer, she would never really leave Manderley.